The man, whose name has not been released, entered the Adelaide River to unsnag his line when he was taken by the saltwater crocodile, Northern Territory Police Duty Superintendent Jo Foley said.
The woman did not see her husband taken but heard "a scream and then turned around and saw a tail splashing in the water," the officer said.
The Adelaide River crocodiles are a major tourist attraction. The man was attacked near the Arnhem Highway bridge close to where cruise ships show sightseers crocodiles leaping from the water to snatch chicken carcasses suspended from poles.
Police said searchers in boats found the victim's body on Monday night and shot the crocodile.